<!DOCTYPE HTML>
<html>
<body>

  <script>

    let urls = [
      'https://api.github.com/users/iliakan',
      '/',
      'http://no-such-url'
    ];

    Promise.all(
        urls.map(url => fetch(url).catch(err => err))
      )
      .then(responses => Promise.all(
        // if it's an error then pass on
        // otherwise response.json() and catch errors as results
        responses.map(r => r instanceof Error ? r : r.json().catch(err => err))
      ))
      .then(results => {
        alert(results[0].name); // Ilya Kantor
        alert(results[1]); // SyntaxError: Unexpected token < in JSON at position 0
        alert(results[2]); // TypeError: failed to fetch (text may vary)
      });
  </script>

</body>
</html>
